88 points | by westurner19 小时前
I would however like to see that waste heat being used for something like dishwashers or just being vented out (instead of into the room that might have to be actively cooled).
Water heaters that are also AC units do exist (a heat pump is an ac run backwards)
I could imagine at some point, all our heated and cooled air, water, and ice could be one system.
For fast temperature demands, such as hot water or ice, perhaps reservoirs of chemically stored heat and cold could be built up at useful locations, for very high speed release when needed.
Completely dispense with storing hot or cold air/water, except for fridges. But provide the cool air for them, as a byproduct of being one system, avoiding the local inefficiency of both cooling air in small quantities and generating heat at the same location.
It would make it cheaper to have more fridges and ice makers around a houses, if you just had to plug them into power and an HVAC controlled "inlet/outlet".
That's an average power consumption of 20W. But electric heaters are say 1200W or 2000W.
Or perhaps you may have missed a nuance in the comments above yours? Nobody is claiming that heat pumps don't work, they certainly require a source of heat to pump though, and the air in a kitchen fridge ain't that.
https://www.homedepot.com/b/Plumbing-Water-Heaters-Tank-Wate...
You could save some power, but not very much.
I've always wished for a fridge that was mounted to an exterior wall. In the summer, it operates like a normal fridge but with the condenser coil outside of the house. In the winter, the compressor system turns off when the outside temp goes below a certain value and little door/shutters with fans regulate the temperature of the refrigerator either by letting in cold air from outside (if the interior needs to be colder) or from the inside (if the interior needs to be warmer to prevent food from freezing).
There's probably a few good reasons why this is not actually practical but I'm tempted to try something like it in retirement.
So if you really need to push indoor air inside to avoid that, you are basically killing the efficiency. And not only that, you would push warm and comparibly humid air inside the fridge a lot. It will condense and now your fridge has to deal with a lot of condensation and probably get moldy.
But good to see that I'm not the only one making these thought experiments.
My personal conclusion is: eventually we will have a single refrigerant distribution system where other systems can be connected and then make use of it (similar to multi-split ACs, but extended to more devices). Then, your fridge would just be part of the system.
And, just to understand: transferring heat from inside the fridge to the outside in the case that the outside is colder is so energy efficient already, there's no need at all to optimize anything. A solar panel as big as your hands will be sufficient even in winter to take care of keeping the fridge cool. That's how little energy is needed.
However, it probably doesn't pan out.
An energy star fridge uses about 400kWh/year. In pittsburgh, we have 5710 cooling degree days and 736 cooling degree days. Those cooling degree days are spread across about 4 months. So we only need to dump heat from the refrigerator about 1/3 of the time: 133kWh. With an A/C CoP of 5, that means that cooling the extra load from your fridge costs you about an extra 26kWh / year, or about $5.
On the heating side, it's actually better to heat the house from the fridge than to burn gas - you've basically got a heat pump system! Heat pumps are more efficient than direct heating. If you already have an efficient heat pump system this may not be as true but it probably comes out in the wash.
The physical modifications to the house would have to be very cheap to make this cost-effective -- and more penetrations through the house envelope create opportunities for leaks.
You can see an example in this 1920s Frigidaire training video (which is also worth watching for other reasons): https://www.youtube.com/watch?v=W-t7DqOAMME
Even in parts of Europe and Iceland with ready access to a common municipal heat exchange, household refrigerators don't have have enough heat output to justify the infrastructure.
The typical domestic fridge just needs to "get cold once" and the remainder of its duty-cycle (aside from the rare holiday feast or party) it's just trickle-cooling.
https://en.m.wikipedia.org/wiki/Johnson_thermoelectric_energ...
This is great stuff to research, but trying to market them for potentially slightly more efficient refrigerators seems like going for the highest fruit on the tree.
I thought paving the way meant a clear path to the end goal, because you already know the route and all the necessary engineering to get there.
But upping the effect from 0.1c to 1.7c is pretty good. I doubt there's a lot more to come from this, so i doubt the path finding too.
It seems like older fridges worked really really well and last a long time.
The "last a long time" bit might be survivorship bias. They might last a long time (or not) but having one old working fridge does not prove reliability.
As far as I know, there was no ban on using old fridges and I don't think people usually throw away major appliances that work.
You also have to consider its cooling capacity, you only need a little bit of cooling 95% of the time, but when you put fresh groceries in it or water in the fridge, until those are cooled down they are heating up everything else in the fridge and so stuff will spoil faster/easier. Some older fridges might take a long time to cool everything down if you put in more than a single item at a time.
But really, most fridge breakdowns are not because of a compressor failure or anything major, 99% of the time it is some simple electronic component. A simple bad capacitor can prevent your fridge compressor from kicking in. Or a thermocouple could go bad and not tell it to turn on when it should. Both of those parts cost like $2 to produce, but of course they choose more proprietary designs and configurations to make a generic fix more difficult which lets them markup the parts on prices. Which has the side effect of convincing more people to just buy new because they don't know if the 1500% marked up proprietary part was the only part near failure, and they don't have the knowledge or confidence to start tinkering on their refrigerator before they lose all their potential savings on spoiled food, or use an appliance repairman who will add on $200+ onto the inflated parts prices because they don't want the liability taken upon themselves if they were not using direct replacement parts.
Whatever happened to acoustic cooling?
Did peltiers ever get efficient?
Not compared to gas compression. For a relaxed take on it:
https://youtu.be/CnMRePtHMZY?si=jusDm81RWkDF_HJ0&t=900 (Thermoelectric cooling: it's not great)
Though part of the complaints about the mini fridge is due to lack of insulation. But he compares it to his usual fridge, which has a similar power draw as this 60W mini fridge, and there's a 50x difference in volume to cool.